To solve inverse matrix problem, the first row 3-20-1, the second row 0-22-1, the third row 1-2-3-2 and the fourth row 0-12-1 of fourth order matrix are used to solve inverse matrix problem

To solve inverse matrix problem, the first row 3-20-1, the second row 0-22-1, the third row 1-2-3-2 and the fourth row 0-12-1 of fourth order matrix are used to solve inverse matrix problem

Let's note that a = 3 - 20 - 10 22 11 - 2 - 3 - 20 12 1 Change (a, e) into (E, P) P by row transformation, that is, the inverse matrix of a ^ (- 1) (a, e) = 3 - 20 - 1 1 1 000 2 2 1 0 01 - 2 - 3 - 2 001 1 2 0 01 R 1 and R 3 exchange 1 - 2 - 3 - 2 001 2 1 0 01

The inverse matrix of matrix A = {1,0,0; 0,2,0; 0,0, - 3}

1 0 0 1 0 0
0 2 0 0 1 0
0 0 -3 0 0 1
1 0 0 1 0 0
0 1 0 0 1/2 0
0 0 1 0 0 -1/3
The inverse matrix is as follows
1 0 0
0 1/2 0
0 0 -1/3

As shown in the figure, we know two concentric circles with point o as the common center. The chord ab of the big circle intersects the small circle with C, D. (1) prove: AC = db; (2) if AB = 6cm, CD = 4cm, find the area of the ring

(1) Through the point o as OE ⊥ AB in E, ≁ AE = be, CE = De, ≁ ae-ce = be-de, ≁ AC = BD; (2) connect OA, OC, in RT △ AOE and RT △ OCE: oe2 = oa2-ae2, oe2 = oc2-ce2, ≁ oa2-ae2 = oc2-ce2, ∵ oa2-oc2 = ae2-ce2, ∵ AB = 6cm, CD = 4cm, ≁ AE = 3cm, CE = 2cm

13.7 × 17 / 31 + 19.8 × 17 / 31-2.5 × 17 / 31 using factorization,

13.7×17/31+19.8×17/31-2.5×17/31
=(13.7+19.8-2.5)×17/31
=31×17/31
=17

BD and CE are bisectors of triangle ABC, which intersect at point O. if the angle BOC = 138 degrees, then the angle A=

boc=90+1/2 a
So a = (138-90) * 2 = 96 degree

Simple algorithm 19.82 + 16.4 minus 9.8

19.82+16.4-9.8
=19.82-9.8+16.4
=10.02+16.4
=26.42

What is upper trigonometric determinant? Lower trigonometric determinant

The upper triangular determinant is a determinant whose elements below the diagonal are equal to 0
The lower triangular determinant is just the opposite

How much is (x-75) divided by 20 = (x + 100) divided by 15

(x-75) divided by 20 = (x + 100) divided by 15
Double 60
3(X-75)=4(X+100)
3X-225=4X+400
3X-4X=400+225
-X=625
X=-625

What is the limit of X · sin (1 / x)
Is limx · sin (1 / x) not equal to Lim sin (1 / x) / 1 / X when x → 0? So according to the important limit Lim SiNx / x = 1, isn't the original formula equal to 1?

The answer is 0
Is limx · sin (1 / x) not equal to Lim sin (1 / x) / 1 / X when x → 0
Lim SiNx / x = 1 holds when x approaches 0
After substitution, X tends to infinity, and infinitesimal * bounded quantity = infinitesimal is applied

Simple calculation of 3.2 × 5.8 △ 0.16

3.2×5.8÷0.16
= 3.2÷0.16×5.8
= 20×5.8
= 116